Probability of Getting Drafted by Star-Rankings and Ramifications of Arbitrary 5-Star Designation

As many college football fans follow recruiting and its relative importance to winning championships, the understanding that recruiting ratings (which largely determine star-ranking status) are a good approximation of team talent. This article is even more evidence that the rankings do a good job of identifying high school talent.

From my point of view, the NFL draft is the best measure of whether a player is talented or not. NFL teams spend a lot of money, time , and opportunity cost on each draft pick. As such, they have the most skin in the game and (presumably) relevant expertise in talent evaluation.

This article outlines the probability of getting drafted by using a more granular star-ranking (https://thefaircatch.com/2021/06/11/a-more-granular-view-of-star-rankings/), which is an expansion of the 247 Composite ratings. Furthermore, it highlights a possible ramification to the arbitrary cutoff of approximately 30 five-star players in each cycle.

Data

Recruiting class data and NFL draft data were obtained from http://www.collegefootballdata.com. These data sets spanned the years 2005 to 2021. There were 53,826 high school rated players and 2,307 records for drafted players.

Using a more granular breakdown of star-rankings provided insight as to where players draft propositions started to diverge.

In looking at the above scatterplot, a few things become noticeable. First, there is a visible cutoff at the 5.0 star-ranking in the upper left quadrant, which represents earlier-round draft picks and highly rated recruits. This is like because of the arbitrary 30-player limit to 5-star status. It pushes good players down into the high 4-star range.

There is also a clear diminishing presence of higher-rated players to the right of the vertical line (mean line for draft pick).

Below the mean line for star-ranking, things look fairly uniformed.

Probabilities

My hypothesis is that the arbitrary cutoff for 5-stars artificially divides them from 4-stars. The stacking up of data points along the 5.0 star range supports this belief. In looking at further breakdowns of the data, this hypothesis continues to be supported.

Taking all of the 53,826 observations against the NFL draft data and breaking it out by incremental star-rankings, the probabilities for each category getting drafted is shown in the bar graph above. To achieve even a 10% overall chance of getting drafted, a player needs to be a 4.2 star, or have a composite rating of 0.9087 at a minimum. To have a 20% chance of being drafted, a player should be a 4.9 star, which is a composite score of 0.9738.

Also visible here again, is the bottleneck right at the five-star cutoff, strengthening the case against the arbitrary 5-star cutoff.

Drafted by Round

Just getting drafted is a huge marker of success in my view. But getting drafted in early rounds is that much better.

In the bar graph above, the round drafted proportions are added. Once again, players at the 4.9 star rating are considerably more likely to be drafted in the first two rounds. Below, I broke these out by NFL draft round

Conclusion

It’s pretty clear that better players out of high school are more likely to get drafted, and more likely to get drafted earlier in the draft. However, the arbitrary ~30 player cutoff for 5-star designation strikes me as a marketing and hype gimmick. Unfortunately, this probably denies some very deserving players of the five-star status.

Based on what I’ve found, the 5-star designation should be awarded to any player with a composite rating score of ~0.9738, which would give them a 20% chance of being drafted.

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